Question

A solution contains some or all of the ions Cu²⁺, Al³⁺, K⁺, Ca²⁺, Ba²⁺, Pb²⁺, and NH₄⁺. The following tests were performed, in order, on the solution.

1.Addition of 6 M HCl produced no reaction.
2.Addition of H₂S with 0.2 M HCl produced a black solid.
3.Addition of (NH₄)₂S produced a white solid.
4.Addition of (NH₄)₂HPO₄ in NH₃ produced no reaction.
5.The final supernatant when heated produced a purple flame.
Identify which of these ions were present in the solution (P), which were absent (A), and which were inconclusive (I)
a. Cu²⁺
b. Al³⁺
c. K⁺
d. Ca²⁺
e. Ba²⁺
f. Pb²⁺
g. NH₄⁺

Answer 1

Among given, the ions which are present in the given solution are:

Cu²⁺, Al³⁺ and K⁺

Among given, the ions which are absent in the given solution are:

Pb²⁺, Ca²⁺ and Ba²⁺

The ion which no conclusion is NH₄⁺.

Step-by-step explanation:

Reagents given are used in salt analysis. The salt analysis is a qualitative analysis used for the identification of cations and anions of inorganic salts.

HCl is used for the identification of group I cations. As no reaction occurred when HCl is added to the solution, that means group I cations are absent.

So, among the given Pb²⁺ is a group I cation, therefore, Pb²⁺ is absent.

H₂S along with HCl is used for the identification group II salts.

Addition of Addition of H₂S with 0.2 M HCl produced a black solid, so, group II cation Cu²⁺ is present.

H₂S is used for the identification of group III cations.

When H₂S is added to the filtrate of group II, white precipitate is formed that means group III cations are present. Among group III cations, Al³⁺ is present.

Addition of (NH₄)₂HPO₄ in the presence of NH₃ is used for the identification of group IV cations.

As no precipitate is formed, therefore, group IV cations are absent.

So among given options, Ca²⁺ and Ba²⁺ are absent in the given solution.

The final supernatant when heated produces purple flame which indicates the presence of K⁺.

Therefore, among given, the ions which are present in the given solution are:

Cu²⁺, Al³⁺ and K⁺

Among given, the ions which are absent in the given solution are:

Pb²⁺, Ca²⁺ and Ba²⁺

The ion which no conclusion is NH₄⁺.